title: Signal-on impedimetric electrochemical DNA sensor using dithiothreitol modified gold nanoparticle tag for highly sensitive DNA detection.
abstract: A signal-on impedimetric electrochemical DNA (E-DNA) sensor using gold nanoparticles (AuNPs) as tag was developed for highly sensitive detection of DNA hybridization. A probe ssDNA (PDNA) was immobilized by forming an amide between the -NH2 moiety at the 5'-terminus of PDNA and the -COOH group at self-assembled 11-mercaptoundecanoic acid on a gold electrode. Subsequently, AuNPs were attached to the -SH moiety at the 3'-terminus of the immobilized PDNA by S-Au interaction, and then functionalized with -OH by immersing the electrode in dithiothreitol solution. In the absence of the target DNA, the flexible single-stranded PDNA supports efficient contact between AuNP tag and electrode, ensuring a low electron transfer resistance (Ret) of the E-DNA sensor using the [Fe(CN)6](3-/4-) redox probe. Upon hybridization, a rigid probe-target duplex is formed, which pushes the AuNP tag away from the electrode and increases the distance between AuNP tag and the electrode, thereby increasing the Ret of the E-DNA sensor. Based on hybridization-induced conformational changes, the E-DNA sensor shows an increased Ret response when the target DNA concentration is increased from 5 fM to 500 pM. Furthermore, the E-DNA sensor showed differentiation abilities for single-base mismatch.
authors.affiliation: Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi'an 710062, China.
authors.forename: Cuiping
authors.initials: C
authors.lastname: Wang
authors.forename: Xiaqing
authors.initials: X
authors.lastname: Yuan
authors.forename: Xuhui
authors.initials: X
authors.lastname: Liu
authors.forename: Qiang
authors.initials: Q
authors.lastname: Gao
authors.forename: Honglan
authors.initials: H
authors.lastname: Qi
authors.forename: Chengxiao
authors.initials: C
authors.lastname: Zhang
mesh_terms: D015374:Biosensing Techniques / Q000379:methods*; D004247:DNA / Q000032:analysis*; D004229:Dithiothreitol / Q000737:chemistry*; D004563:Electrochemistry; D005821:Genetic Techniques; D006046:Gold / Q000737:chemistry*; D057230:Limit of Detection; D053768:Metal Nanoparticles / Q000737:chemistry*; D046529:Microscopy, Electron, Transmission; D008958:Models, Molecular
chemical_list: D006046:Gold; D004247:DNA; D004229:Dithiothreitol
keywords: Au nanoparticle; DNA; E-DNA sensor; Impedimetric; Signal-on